- Category: Blog
- Published: Wednesday, 07 December 2016 16:35
- Written by Jack Wilbur
- Hits: 1962
Tomorrow, December 8, 2016, marks the one year anniversary of the UDAF aquaponic demonstration garden in the lobby of our main building in Salt Lake City. The vision of Utah Commissioner of Agriculture and Food, LuAnn Adams, the garden is designed to inspire people, home gardeners and farmers alike. "This is and will be a great way to grow food as demands on water resources and land increase," said Adams.
As you can see from the photos we have come a long way in a year. We've had some great successes and a few bumps over time. But as a demonstration garden we welcome the challenges so we can learn from them and hopefully educate others who are thinking of starting a hydroponic or aquaponic garden or farm of their own. For this anniversary blog post we decided to delve into the system, the successes and the setbacks, briefly. We could write a book from what we have learned in a year, but we will spare you a lot of the details and try to stick to the highlights.
We started a year ago by constructing the main aquaponic system. The 150 gallon tank to the left contains the hybrid striped bass that we use to provide the fertilizer for the produce that reside in the eight rails above. The other two tanks each hold 75 gallons. The middle tank is actually a mixture of lava rock and water. It is the pass-through bio filter for the system. The waste product from the fish is converted into usable nitrogen (nitrate) that fertilize the plants. We will talk a little more about the fish and the bio filter in the setbacks section. The tank to the right is the pump tank. An 800 gallon per hour submersible pump moves the water up to the top rail on each side. Gravity and pressure distributes the water down to each of the lower rails and then back into the fish tank. There are 11 3-inch holes in each of the eight rails. Special 3-in. net cups fit perfectly into the holes and hold the plants. The rail system holds 88 plants.
Additionally, In January 2016 we added a two inch thick piece of rigid foam insulation material which floats on half of the pump tank. It has 11 holes cut into it for plants. Along with the aquaponics garden, we have over the months started several small self-contained hydroponic systems. As you may know, there are many styles of water based gardens including floating rafts and grow beds, and vertical systems like our rails and towers, which we will discuss in a bit. What distinguishes aquaponics from hydroponics is the source of the plant food. Fish are present as the fertilizer source in aquaponics and hydroponics uses special fertilizers that are added periodically to the system. Over time we have added three five gallon buckets, each of which is its own hydroponic system. Each bucket holds one large tomato plant. There are also two towers, which we will briefly mention when we discuss setbacks. Finally we recently added a smaller plastic storage container that has a lid with six plant holes drilled into it. Though it is new to us it seems to work well. We will mention it more in the successes section.
When we first started we added fish before the bio filter was active. We now know that there is an enzyme product you can buy anywhere you can get aquarium supplies that will help start or activate the biol filter so it can convert the ammonia from the fish into nitrite and then into nitrate. Not only will the plants not take up the ammonia and nitrite, they are toxic to fish. If they have not been converted to nitrate before returning to the fish tank the fish will get sick and die. Approximately 45 fish met their untimely end that way. Another 25 or so died in late June when our water pump suddenly went out. At the time the return water flow dropping through the air a foot or so from the bottom rails was the only source of aeration or oxygen in the fish tank. The plants survived a few hours without water flow, most of the fish did not. That day we installed air pumps and air stones that make oxygen-rich bubbles in the water. That is an additional source of oxygen. We now have about 25 fish that we got from the Utah Division of Wildlife Resources in early July. They are doing great and growing quickly.
The tower units we built have been a real challenge. Towers fall into the category of aeroponics, which refers to how the plants receive water. In the rails, floating rafts, grow beds and our storage container, the roots of the plants are always submerged. Movement of the water or bubbles in the water provide the aeration needed for plant growth. In aeroponic systems the roots are suspended in air and water drips onto the roots. This is the most advanced and challenging way to grow plants hydroponically. That may be part of the reason we have killed scores of plants in the two towers we have built. Another issue may have to do with light and lighting. They are hard to light 100 percent artificially because of their vertical nature. We recommend having an area with at least some natural direct light if you are going to use a tower. We are going to keep trying with ours. Hopefully we will have some successes to report during year two.
We have struggled with certain types of crops in all of our systems. Strawberries are the most notable example. Kale has not performed as well as expected, nor has spinach. However, most of our crops have done well, as we note below.
Our current group of fish has been with us nearly six months and we haven't killed any of them yet. We'll take that as a success. Additionally, after a slow start with the plants they are now growing at rates closer to what we expected. Head lettuce varieties that are supposed to take about 60 days from seed in soil are now taking us about 45 days. We hope to cut by a few more days. Leaf lettuces that are rated at 30-50 days to start harvesting leaves are taking us slightly less time, though the difference is not as significant as we would like. Depending on the time of year we have grown 50-75 lettuce plants at a time in the system. We have harvested about 50 heads of lettuce and nearly 30 8-10 ounce bags of dry leaf lettuce.
We have also harvested 15 bunches of Swiss chard from 4-6 plants, 10 small bags of basil from 2-3 plants and 10 pounds of cherry tomatoes from four plants. Our one tomato plant that produces larger, 6-8 oz. fruits has yielded nine tomatoes to this point.
As we mentioned in the setbacks section, the vertical towers have mostly disappointed us so far, but the storage container, the floating raft and the rails are all performing nicely. We have room to add another storage container or two. At about $40 each for a 6-8 plant station unit, they are well worth the investment.
Though we are not fully happy with our harvest numbers we are encouraged by the performance of the garden during the second half of the year, and now as winter approaches it continues to look lush and green, and we are still harvesting tomatoes, lettuce and other items.
Commissioner Adams Harvesting tomato and basil in July.